The objective of this project is to study the biology of human pathogenic Leishmania in their phlebotomine sandfly vectors. The project involves the disciplines of parasitology, medical entomology, genetics, virology, biochemistry and immunology. Laboratory-reared sandflies will be experimentally infected, with a number of different Leishmania types and the following aspects of the parasites biology in the insects will be studied: the role of sugars in the enhancement or inhibition of leishmanial infection in sandflies, the effect of avian blood on the parasite infection in the vector, the genetic basis of vector competence in sandflies, biochemical and morphological studies of the sandfly hind gut and its role in the transmission of Le. braziliensis group parasites, and the possibility that genetic recombination might occur among related Leishmania types in the insect vector. A newly discovered sandfly cytoplasmic polyhydrosis virus will also be characterized and evaluated as a possible biological control agent for leishmaniasis.